The invention relates to a gas bag protection device with gas bag to which two opposing plies of fabric are assigned, which are sectionwise connected to each other by integral interweaving.
Especially large-area side gas bags, so-called window bags, have two plies of fabric which form the outer walls of the gas bag and are connected to each other at the rim and in the region of partition walls between neighboring chambers by integral weaving. The loading of the threads in the durably woven section, for example in the region of the rim, is very high just when the first pressure shock occurs on inflation. In the case of window bags it is always attempted to optimize gas guidance for rapid inflation and to adapt the hardness of the gas bag to the ambient conditions.
The invention provides a gas bag protection device with gas bag making it possible by simple and cost-effective means to quickly and simply adapt the gas bag geometry, the flow conditions within the gas bag and to reduce thread loading in the durably woven sections without involving additional steps in fabrication. This is achieved in a gas bag protection device with gas bag to which two opposing plies of fabric are assigned. The plies of fabric consist of warp and weft threads and are sectionwise connected to each other by integral interweaving so as to form at least one inflatable chamber. The plies of fabric are integrally interwoven in a portion by at least one of the warp and weft threads in such a manner that the at least one thread forms a sacrificial thread which bursts in a restraint situation. In gas bags known hitherto, use is made of so-called burst seams designed to intentionally burst on inflation or deployment of the gas bag. These burst seams are formed, for example, of a less tough thread, it being very difficult, however, to reliably reproduce or predict the load at which the thread bursts. On top of this, separate steps in fabrication were needed, for example, additional stitching. In the gas bag protection device in accordance with the invention, by contrast, it is possible to join the plies of fabric to each other by one or more sacrificial threads in small punctiform or, for example, also linear areas by simple and cost-effective integral weaving. The sacrificial threads are destroyed by the increase in pressure within the gas bag by it being inflated or by the occupant diving into the gas bag.
Integral weaving is done in the so-called Jacquard weaving technique.
In accordance with the preferred embodiment the gas bag comprises two opposing plies of fabric connected to each other at the rim of the gas bag, preferably by integral weaving. The plies of fabric delimit at least one chamber which can be filled with gas, they being integrally interwoven sectionwise, for example, as mentioned, to form the rim or to form partition walls. By means of the sacrificial thread the plies of fabric are connected to each other in the region of an inflatable chamber, i.e. within the gas bag.
The destructible portion thus formed may be made use of for various purposes and accordingly can be arranged at differing locations.
A first possibility provides that a chamber is separated by the sacrificial thread, which chamber, in terms of flow, is to be filled later than a neighboring chamber. The sacrificial thread separates the two chambers from each other; however, as soon as the pressure in the first-filled chamber is sufficiently high, the sacrificial thread bursts and the gas is able to flow over into the neighboring chamber. Such an overflow may occur in any case or, for example, not before a gas bag pressure is attained which can only be produced by the impact of the occupant. In this case an outflow opening may also be provided in the chamber to be filled later permitting the gas to escape to the environment. This is important especially in the case of side gas bags which need to be gas-tight and for this purpose are coated with a film so that the gas bags are not too hard.
Another possibility of making use of the sacrificial threads consists of providing them to damp the first pressure shock which acts on the durably woven sections where it results in extreme loading of the threads. When the sacrificial threads are located at a predetermined distance upstream of a durably woven section this abrupt loading of the fabric in this section is significantly diminished.
A third possibility of making use of sacrificial threads is to employ them for guiding the gas flow. Thus, the sacrificial threads may run linearly, for example, and guide the gas on commencement of inflation into a chamber or within a chamber into specific portions, thus enabling deployment and inflation to be optimized by simple means.
A fourth possibility of making use of sacrificial threads consists of, for example, employing them to close off not the gas bag itself, but a ply of fabric, serving as the cover of the gas bag and enveloping the gas bag in the folded condition and maintaining it in this condition. Thus, it is provided an envelope which may be used as a transport envelope or a built-in-envelope.